Engine starter gear devices operate in an extremely hostile work environment. The starter is usually bolted to the engine with the pinion gear adjacent to the ring gear. In most automotive applications, the starter is secured to the engine so as to permit access and serviceability from the bottom of the vehicle or underneath the engine. Because of these considerations, the starter motor and more particularly the starter gearing is subjected to dirt, dust, rain, snow, ice, salt, moisture, corrosion, heat, cold and oil. In spite of this work environment, the starter gearing device must perform several critical funtions in an extremely short period of time, if the engine is to be started satisfactorily. These critical functions include shifting, indexing, driving overrunning and disengagement when the engine becomes self-operative.
The prior art developments have resulted in engine starter gearing devices having a unidirectional torque transmitting clutch. In addition, the prior art starter gearing devices also include a mechanism for indexing the pinion gear of the starter with the engine's ring gear when an abutting condition exists between the pinion gear and the engine ring gear. Finally, the prior art starter gearing devices include mechanisms for separating the clutch teeth within the starter when the pinion gear of the starter rotates at a faster speed than the starter shaft. However, because of the hostile work environment of the starters, it has been found that the pinion gear cannot be permitted to rest directly on the armature shaft, especially in cold weather when fine matter, oil and moisture tend to freeze on the shaft. It has been found that these obstructions on the armature shaft can restrict the axial travel of the pinion gear and cause the pinion gear to index prematurely, that is, before the pinion gear abuts against the ring gear. This can cause milling of the engine ring gear and premature failure of the starter.
In some prior art starters, for example, U.S. Pat. No. 3,263,509 issued to Digby on Aug. 2, 1966 and owned by the assignee of the present patent application, a sleeve member is mounted between the pinion and the armature shaft to eliminate the relative motion between the armature shaft and the pinion gear. Thus, the sleeve member, as it is moved axially on the armature shaft, scrapes the outer diameter of the armature shaft to remove the dirt, moisture, etc. thereon without causing the pinion gear to index prematurely. The use of a sleeve member, however, severely restricts the choice of pinion size and because of this physical constraint prevents the use of smaller pinion drives on such starter devices.
Other examples of prior art engine starter gearing requiring a sleeve member between the armature shaft and the pinion are shown in U.S. Pat. No. 3,905,245 issued to Harold Mortenson on Sept. 16, 1975, owned by the assignee of the present patent application; U.S. Pat. No. 3,915,020, issued to Irving Johnson on Oct. 28, 1975, owned by the assignee of the present patent application; and U.S. patent application Ser. No. 132,012 filed on Mar. 20, 1980, by Harold O. Mortenson.
None of the aforementioned prior art designs has been able to eliminate the use of a sleeve member between the armature shaft and the pinion because dirt or other obstructions on the armature shaft could make the pinion gear index prematurely. Thus, none of the aforementioned designs is able to reduce the physical size of the pinion member in order to permit the use of small pinion gear designs for small drive applications which do not index prematurely when dirt, oil, water, etc. adhere to the exterior of the armature shaft.